a) Find of the Invention
The invention is directed to a secondary air nozzle for furnaces with a curved base body provided with pins for holding a ceramic protective casing.
b) Background Art
It is known to arrange curved secondary air nozzles in the cover of the furnace body above the front edge of the feed table. These secondary air nozzles emerge vertically from the furnace body cover and are aligned at an inclination of roughly 75.degree. toward the furnace body. Because a high concentration of low temperature carbonization gases are encountered in this region, secondary air is introduced in this region to enable combustion of these gases. Since these low-temperature carbonization gases are very aggressive, secondary air nozzles made of metal are subject to intensive corrosion. In order to protect these nozzles against corrosion it is known to provide a protective casing of ceramic material. A plurality of radially projecting pins are welded on the outer casing of the secondary air nozzle so as to hold the ceramic body at the outer casing of the secondary air nozzle. This provides a largely satisfactory protection against corrosion, but the useful life of such secondary air nozzles is nevertheless limited because the feeding of fuel, particularly refuse, causes banked-up masses of fuel to be pushed past the nozzle so that the ceramic casing is destroyed by mechanical action, which results in accelerated corrosion of the secondary air nozzle. The pins for holding the ceramic bodies are exposed as a result of mechanical damage and corrode first at an accelerated rate so as to undermine the support of the ceramic bodies, thus accelerating the mechanical destruction of the protective casing with ensuing corrosion of the secondary air nozzle.